Heating element assemblies for use in water heaters and the like are illustrated in U.S. Pat. Nos. 4,152,578, 3,943,328, and 3,217,138, which are conventional insofar as they illustrate sheathed heating elements mounted in a mounting plug of either the screw type or surface mounted type. It has been proposed in U.S. Pat. No. 3,943,328, to use a sheath of thermal-plastic material to enclose an electric resistance heater element. The patent states, "of course, if a water tank should run dry, the plastic sheathed heater would not be subjected to the modifying effects of the water and therefore the thermal plastic material would melt and the heater would not be subjected to the modifying effects of the water and therefore the thermal plastic material would melt and the heater would fail, but metal sheathed heaters under these circumstances would also fail. The failure of a heating element or its being energized when not submerged in conventional steel or glass lined tanks will not affect the tank itself, ordinarily. However, with the advent of plastic hot water tanks, conventional electric water heater elements are liable to damage the tank permanently if the heating element were energized in a dry tank.
One of the objects of this invention is to provide a water heater element assembly that can be used safely in a plastic hot water tank.
Another object is to provide such a water heater element assembly that can be manufactured easily, is rugged, dependable, and long-lasting.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawing.